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May 3, 2012 Alfalfa Magic Valley - Idaho
Below is information about Clover Root Curculio in forage alfalfa. The information is being provided by Dr. Erik Wenninger, UI Extension Entomologist and Dr. Glenn Shewmaker, UI Extension Forage Specialist. Both are located in Kimberly, Idaho.
There are a lot of questions about clover root curculio in forage alfalfa, but not a lot of information.Review the attached pdfs, especially the CRC fact sheet attached for more information. There isn’t a lot of new information about this pest, the entomologists who have worked on this have all retired.
Considerations for management of clover root curculio:
1. There are no registered pesticides for control of the larval stage of clover root curculio on alfalfa forage.
2. There are pesticides registered for use against adults on alfalfa forage, but adulticides are not likely to provide effective control because adults move readily among fields and are active over a long time period. The larval stage is most damaging.
3. Larvae produce the most damage and usually it is a year later that you see the symptoms in the early spring after alfalfa breaks dormancy.
4. Symptoms of CRC larval feeding damage are:
a. Patches of slow, dormancy-breaking alfalfa, sometimes related to irrigation management and drought. Drought exacerbates the water and nutrient uptake in alfalfa because of the trimming of fine roots in alfalfa and feeding on the nodules which reduces N fixation temporarily.
b. Individual weak plants with the patches, with some more healthy appearing plants side by side.
c. Scoring and girdling of alfalfa roots by the later stages of larvae.
5. Recommendations for control:
a. Since no pesticides are registered, we must rely on cultural control methods.
b. Rotation is the key method.
i). Rotation of an alfalfa field to a non-host crop (i.e., any crop other than alfalfa or clover) will eliminate larval food sources and discourage adults from laying eggs in the soil.
ii). New alfalfa fields should be planted as far away as possible from existing alfalfa fields, especially those with confirmed CRC infestations.
c. New plantings made during the spring may be less susceptible to CRC than those made during the fall, since many spring-planted alfalfa emerges towards the end of adult CRC activity, and should have a year of growth before it might be attacked by CRC larvae. Fall-planted alfalfa will have less time to mature before potential attack the following spring, and may also be more susceptible to possible attack by adults during fall establishment.
d. Our variety trials have not been directly assessed for CRC resistance, but most alfalfa breeders don’t think there are any resistant varieties identified, and no one seems to directly select for resistance to CRC.
e. Irrigation and fertility management will reduce the negative effects of CRC root damage. Although N application to provide N to nodule-affected plants is probably not economical since that condition seems to be very temporary.
f. The studies from Montana do not show consistent benefit from (UNREGISTERED FOR CRC) Furadan, although adult CRC numbers were reduced.
g. CRC larvae control would be difficult.
6. ID of adults and larvae
a. Damage by adults on the alfalfa leaves can be found occasionally, and relatively small numbers of adults have been found at Kimberly. Damage by adults is not likely to be economical unless heavy infestations attack newly planted alfalfa during the fall.
b. Larval damage has been observed throughout Idaho and extensively in the Kimberly area.
c. We have not been able to ID or find larvae in spring at Kimberly, although timing of looking for larvae and depth in the soil are a guess.
Posted By: Jerry Neufeld
May 4, 2012 Alfalfa Seed Treasure Valley - Idaho
The following information was provided by Dr. Jim Barbour, IPM Specialist at the UI Parma R and E Center.
The Lygus degree day calculator hosted by Integrated Plant Protection Center at Oregon State University and the IPM Centers - PNW Coalition (http://pnwpest.org/cgi-bin/ddmodel.pl?spp=lyg) shows that, depending on your location in the Treasure Valley, we have accumulated about 230 days since January 1, 2012. Peak emergence of lygus bug 1st and 2nd instar nymphs should occur right around 272 accumulated degree days: this varies year-to-year, but usually occurs around mid-May, and is the time to begin monitoring for lygus bugs in alfalfa seed fields. In the Treasure Valley that is predicted to occur between May 10 and May 14, depending on your location.
You can monitor degree day accumulation using the link provided above and:
1) Select “ lygus bug [alfalfa seed]Ben Simko 2000” degree day model from the “Select degree day model….” drop down box at the top of the form: the lower and upper temperature threshold boxes (52 and 130 degrees F) and the start and end date boxes (Jan 1 and Aug 31) should automatically fill.
2) In the “Select location” box, select a location in the drop down box best describing your location (e.g. “parma id agrimet” in the “Washington, Idaho” box if you want information for a field near Parma). Make sure “None” is selected in the boxes for the other two locations.
3) Leave the “Or upload your own…” box blank
4) In the “Forecast:” area, enter the zip code or your city and state in the “NWS zip code/city, state” box, or the location nearest your field from the “or weather.com site” drop down box to the right). This selection forecasts 7 days forward based on the local weather forecast (beyond 7 days the forecast is based on the historical average). The predicted date of peak 1st and 2nd instar will vary depending on the forecast location selected, so pick the one closest to your location. Select “none” to have the forecast based only on the historical average.
5) Select the location nearest your field in the “Select historical average forecast location” area. Your selection here should match, as close as possible, your selection in the “Select location” area above: there may not be an exact match. As above, select “none” in the other two boxes.
6) Make sure the “Table” and “Graph” boxes are checked (and the “Include precipitation…” if you want rainfall information) and click the “Calc” button. A table with the current degree day accumulations matching your selection should appear. There should also be a graph near the bottom showing the current year accumulation compared to the historical average for your selections.
Posted By: Jerry Neufeld
May 17, 2012 Alfalfa Treasure Valley - Oregon
Dr. Clint Shock, Superintendent at the OSU Malheur County Experiment Station is reporting that lots of aphids, weevils, and lygus are being found in alfalfa hay fields near Nyssa and Vale. Oregon.
Posted By: Jerry Neufeld
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